Canon EF mount lenses are of the “bayonet” type. This means that the lenses have mounting lugs (three in the case of EOS lenses) which slot into the camera body mount. You then rotate the lens a partial turn to lock it into place with a click.

Most camera makers these days use bayonet-style mounts, though other types were popular in the past. For instance, older Pentax and Leica cameras used screwmount systems - you simply screwed the lens into the camera body’s threaded mount. The lens system used by Canon prior to the introduction of EOS was the FD system, which used a “breechlock” mount system with a rotating friction ring.

Lens hoods often fasten by means of bayonet mounts. Some filters for certain European lenses also use bayonet mounts, though Japanese makers generally use threaded filter mounts.

It’s not clear why the lens mounts are called bayonet mounts. The two theories I’ve heard both stem from bayonets, the knives which soldiers fasten to the end of their rifles. One theory, which is probably utterly apocryphal, suggests it’s a gruesome joke deriving from the instructions given to soldiers on how to use their bayonet - thrust in and twist. The more probable and prosaic theory is that the term derives from the design of bayonet mounts on rifles.